T2.8 vs F2.8 [film/video lenses vs photography lenses]

StructuredAmazing · 15th of November 2010 (Mon)

T2.8 vs F2.8 [film/video lenses vs photography lenses]

whats the difference? do the letters just signify what they are?
like T2.8 and F2.8, do they both gather the same amount of light?

phreeky · 15th of November 2010 (Mon)

My understanding is that the F-stop is the theoretical/true aperture, and the T-stop instead takes all light loss (i.e. from optical elements) into account. A T-stop is the figure you want to use for exact exposure information.

JeffreyG · 16th of November 2010 (Tue)

F-stop is the ratio of the aperture to the focal length. T-stop is the same and includes an offset to account for the amount of light lost in the lens due to transmission losses.

Modern camera lenses have coatings that make losses so small that T-stops are not needed practically any more.

alemerson · 16th of November 2010 (Tue)

http://www.cinema5d.com/news/?p=2575

JPM Photography · 16th of November 2010 (Tue)

http://en.wikipedia.org/wiki/F-number#T-stops

maybe this will help some.

RaZe42 · 16th of November 2010 (Tue)

DxOmark has the t-stops of the lenses they've tested listed. Some people are quite skeptical towards DxO, but things like that should be quite easy to measure, so the results should be reliable. eg the 24-205 f/4 is T5.1, the 24-70 f/2.8 is T3.4.

JeffreyG · 16th of November 2010 (Tue)

Quote:

Originally Posted by RaZe42

DxOmark has the t-stops of the lenses they've tested listed. Some people are quite skeptical towards DxO, but things like that should be quite easy to measure, so the results should be reliable. eg the 24-205 f/4 is T5.1, the 24-70 f/2.8 is T3.4.

How do they account for vignetting? Are they measuring the T-stop at the center of the frame or as an average value?

phreeky · 16th of November 2010 (Tue)

Quote:

Originally Posted by JeffreyG

How do they account for vignetting? Are they measuring the T-stop at the center of the frame or as an average value?

It SHOULD be across the frame. I have seen another website that had the T-stop of a bunch of lenses but cannot remember what it was.

15th of November 2010 (Mon)	#1
StructuredAmazing Member Join Date: Jul 2010 Posts: 603	T2.8 vs F2.8 [film/video lenses vs photography lenses] T2.8 vs F2.8 [film/video lenses vs photography lenses] whats the difference? do the letters just signify what they are? like T2.8 and F2.8, do they both gather the same amount of light? __________________ "Yea, though I walk through the valley of the shadow of death, I will fear no evil" StructuredAmazing forever. My website: Pending...

15th of November 2010 (Mon)	#2
phreeky Goldmember Join Date: Oct 2007 Location: Australia Posts: 3,471	Re: T2.8 vs F2.8 [film/video lenses vs photography lenses] My understanding is that the F-stop is the theoretical/true aperture, and the T-stop instead takes all light loss (i.e. from optical elements) into account. A T-stop is the figure you want to use for exact exposure information.

16th of November 2010 (Tue)	#3
JeffreyG "my bits and pieces are all hard" Join Date: Jan 2007 Location: Detroit, MI Posts: 14,220	Re: T2.8 vs F2.8 [film/video lenses vs photography lenses] F-stop is the ratio of the aperture to the focal length. T-stop is the same and includes an offset to account for the amount of light lost in the lens due to transmission losses. Modern camera lenses have coatings that make losses so small that T-stops are not needed practically any more. __________________ My personal stuff:http://www.flickr.com/photos/jngirbach/sets/ Commercial sports:http://girbach.zenfolio.com/ I use a Canon 5D and 1DIV and a Panasonic GF-1 Gear List: http://photography-on-the.net/forum/...postcount=1550

16th of November 2010 (Tue)	#4
alemerson Member Join Date: May 2010 Posts: 56 IMAGE EDITING OK	Re: T2.8 vs F2.8 [film/video lenses vs photography lenses] http://www.cinema5d.com/news/?p=2575 __________________ 5D Mark II \| 16-35L II \| 24-105L \| 35L \| 50 f/1.4

16th of November 2010 (Tue)	#5
JPM Photography Member Join Date: Apr 2008 Posts: 603 IMAGE EDITING OK	Re: T2.8 vs F2.8 [film/video lenses vs photography lenses] http://en.wikipedia.org/wiki/F-number#T-stops maybe this will help some. __________________ 60D gripped, T2i gripped, Tokina 12-24 f/4, Pentax SMC 50 f/1.4, Nikon Standard Speed Set: 24, 35, 85, 105, 135, 180, Canon 580ex, Calumet Genesis 200 jpmphotovideo.com Please check out my film resume and contact me if you need a DP, AC, or PA for an Atlanta-based shoot.

16th of November 2010 (Tue)	#6
RaZe42 Member Join Date: Feb 2010 Location: Finland Posts: 518	Re: T2.8 vs F2.8 [film/video lenses vs photography lenses] DxOmark has the t-stops of the lenses they've tested listed. Some people are quite skeptical towards DxO, but things like that should be quite easy to measure, so the results should be reliable. eg the 24-205 f/4 is T5.1, the 24-70 f/2.8 is T3.4. __________________ Gear: Canon 5D Mk II \| Olympus 21/3.5 \| Zeiss Distagon 35/2 \| Sigma 50/1.4 ASPH \| Samyang 85/1.4 ASPH \| Canon 100/2.8 L Macro My modest Flickr

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